Mon, 19 Aug 2019 12:47:38 +0200
8229873: 8229401 broke jdk8u-jfr-incubator
Reviewed-by: neugens
1 /*
2 * Copyright (c) 2001, 2015, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
25 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP
26 #define SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP
28 #include "gc_implementation/g1/g1AllocationContext.hpp"
29 #include "gc_implementation/g1/g1Allocator.hpp"
30 #include "gc_implementation/g1/concurrentMark.hpp"
31 #include "gc_implementation/g1/evacuationInfo.hpp"
32 #include "gc_implementation/g1/g1AllocRegion.hpp"
33 #include "gc_implementation/g1/g1BiasedArray.hpp"
34 #include "gc_implementation/g1/g1HRPrinter.hpp"
35 #include "gc_implementation/g1/g1InCSetState.hpp"
36 #include "gc_implementation/g1/g1MonitoringSupport.hpp"
37 #include "gc_implementation/g1/g1SATBCardTableModRefBS.hpp"
38 #include "gc_implementation/g1/g1YCTypes.hpp"
39 #include "gc_implementation/g1/heapRegionManager.hpp"
40 #include "gc_implementation/g1/heapRegionSet.hpp"
41 #include "gc_implementation/shared/gcHeapSummary.hpp"
42 #include "gc_implementation/shared/hSpaceCounters.hpp"
43 #include "gc_implementation/shared/parGCAllocBuffer.hpp"
44 #include "memory/barrierSet.hpp"
45 #include "memory/memRegion.hpp"
46 #include "memory/sharedHeap.hpp"
47 #include "utilities/stack.hpp"
49 // A "G1CollectedHeap" is an implementation of a java heap for HotSpot.
50 // It uses the "Garbage First" heap organization and algorithm, which
51 // may combine concurrent marking with parallel, incremental compaction of
52 // heap subsets that will yield large amounts of garbage.
54 // Forward declarations
55 class HeapRegion;
56 class HRRSCleanupTask;
57 class GenerationSpec;
58 class OopsInHeapRegionClosure;
59 class G1KlassScanClosure;
60 class G1ScanHeapEvacClosure;
61 class ObjectClosure;
62 class SpaceClosure;
63 class CompactibleSpaceClosure;
64 class Space;
65 class G1CollectorPolicy;
66 class GenRemSet;
67 class G1RemSet;
68 class HeapRegionRemSetIterator;
69 class ConcurrentMark;
70 class ConcurrentMarkThread;
71 class ConcurrentG1Refine;
72 class ConcurrentGCTimer;
73 class GenerationCounters;
74 class STWGCTimer;
75 class G1NewTracer;
76 class G1OldTracer;
77 class EvacuationFailedInfo;
78 class nmethod;
80 typedef OverflowTaskQueue<StarTask, mtGC> RefToScanQueue;
81 typedef GenericTaskQueueSet<RefToScanQueue, mtGC> RefToScanQueueSet;
83 typedef int RegionIdx_t; // needs to hold [ 0..max_regions() )
84 typedef int CardIdx_t; // needs to hold [ 0..CardsPerRegion )
86 class YoungList : public CHeapObj<mtGC> {
87 private:
88 G1CollectedHeap* _g1h;
90 HeapRegion* _head;
92 HeapRegion* _survivor_head;
93 HeapRegion* _survivor_tail;
95 HeapRegion* _curr;
97 uint _length;
98 uint _survivor_length;
100 size_t _last_sampled_rs_lengths;
101 size_t _sampled_rs_lengths;
103 void empty_list(HeapRegion* list);
105 public:
106 YoungList(G1CollectedHeap* g1h);
108 void push_region(HeapRegion* hr);
109 void add_survivor_region(HeapRegion* hr);
111 void empty_list();
112 bool is_empty() { return _length == 0; }
113 uint length() { return _length; }
114 uint survivor_length() { return _survivor_length; }
116 // Currently we do not keep track of the used byte sum for the
117 // young list and the survivors and it'd be quite a lot of work to
118 // do so. When we'll eventually replace the young list with
119 // instances of HeapRegionLinkedList we'll get that for free. So,
120 // we'll report the more accurate information then.
121 size_t eden_used_bytes() {
122 assert(length() >= survivor_length(), "invariant");
123 return (size_t) (length() - survivor_length()) * HeapRegion::GrainBytes;
124 }
125 size_t survivor_used_bytes() {
126 return (size_t) survivor_length() * HeapRegion::GrainBytes;
127 }
129 void rs_length_sampling_init();
130 bool rs_length_sampling_more();
131 void rs_length_sampling_next();
133 void reset_sampled_info() {
134 _last_sampled_rs_lengths = 0;
135 }
136 size_t sampled_rs_lengths() { return _last_sampled_rs_lengths; }
138 // for development purposes
139 void reset_auxilary_lists();
140 void clear() { _head = NULL; _length = 0; }
142 void clear_survivors() {
143 _survivor_head = NULL;
144 _survivor_tail = NULL;
145 _survivor_length = 0;
146 }
148 HeapRegion* first_region() { return _head; }
149 HeapRegion* first_survivor_region() { return _survivor_head; }
150 HeapRegion* last_survivor_region() { return _survivor_tail; }
152 // debugging
153 bool check_list_well_formed();
154 bool check_list_empty(bool check_sample = true);
155 void print();
156 };
158 // The G1 STW is alive closure.
159 // An instance is embedded into the G1CH and used as the
160 // (optional) _is_alive_non_header closure in the STW
161 // reference processor. It is also extensively used during
162 // reference processing during STW evacuation pauses.
163 class G1STWIsAliveClosure: public BoolObjectClosure {
164 G1CollectedHeap* _g1;
165 public:
166 G1STWIsAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
167 bool do_object_b(oop p);
168 };
170 class RefineCardTableEntryClosure;
172 class G1RegionMappingChangedListener : public G1MappingChangedListener {
173 private:
174 void reset_from_card_cache(uint start_idx, size_t num_regions);
175 public:
176 virtual void on_commit(uint start_idx, size_t num_regions, bool zero_filled);
177 };
179 class G1CollectedHeap : public SharedHeap {
180 friend class VM_CollectForMetadataAllocation;
181 friend class VM_G1CollectForAllocation;
182 friend class VM_G1CollectFull;
183 friend class VM_G1IncCollectionPause;
184 friend class VMStructs;
185 friend class MutatorAllocRegion;
186 friend class SurvivorGCAllocRegion;
187 friend class OldGCAllocRegion;
188 friend class G1Allocator;
189 friend class G1DefaultAllocator;
190 friend class G1ResManAllocator;
192 // Closures used in implementation.
193 template <G1Barrier barrier, G1Mark do_mark_object>
194 friend class G1ParCopyClosure;
195 friend class G1IsAliveClosure;
196 friend class G1EvacuateFollowersClosure;
197 friend class G1ParScanThreadState;
198 friend class G1ParScanClosureSuper;
199 friend class G1ParEvacuateFollowersClosure;
200 friend class G1ParTask;
201 friend class G1ParGCAllocator;
202 friend class G1DefaultParGCAllocator;
203 friend class G1FreeGarbageRegionClosure;
204 friend class RefineCardTableEntryClosure;
205 friend class G1PrepareCompactClosure;
206 friend class RegionSorter;
207 friend class RegionResetter;
208 friend class CountRCClosure;
209 friend class EvacPopObjClosure;
210 friend class G1ParCleanupCTTask;
212 friend class G1FreeHumongousRegionClosure;
213 // Other related classes.
214 friend class G1MarkSweep;
216 // Testing classes.
217 friend class G1CheckCSetFastTableClosure;
219 private:
220 // The one and only G1CollectedHeap, so static functions can find it.
221 static G1CollectedHeap* _g1h;
223 static size_t _humongous_object_threshold_in_words;
225 // The secondary free list which contains regions that have been
226 // freed up during the cleanup process. This will be appended to
227 // the master free list when appropriate.
228 FreeRegionList _secondary_free_list;
230 // It keeps track of the old regions.
231 HeapRegionSet _old_set;
233 // It keeps track of the humongous regions.
234 HeapRegionSet _humongous_set;
236 void eagerly_reclaim_humongous_regions();
238 // The number of regions we could create by expansion.
239 uint _expansion_regions;
241 // The block offset table for the G1 heap.
242 G1BlockOffsetSharedArray* _bot_shared;
244 // Tears down the region sets / lists so that they are empty and the
245 // regions on the heap do not belong to a region set / list. The
246 // only exception is the humongous set which we leave unaltered. If
247 // free_list_only is true, it will only tear down the master free
248 // list. It is called before a Full GC (free_list_only == false) or
249 // before heap shrinking (free_list_only == true).
250 void tear_down_region_sets(bool free_list_only);
252 // Rebuilds the region sets / lists so that they are repopulated to
253 // reflect the contents of the heap. The only exception is the
254 // humongous set which was not torn down in the first place. If
255 // free_list_only is true, it will only rebuild the master free
256 // list. It is called after a Full GC (free_list_only == false) or
257 // after heap shrinking (free_list_only == true).
258 void rebuild_region_sets(bool free_list_only);
260 // Callback for region mapping changed events.
261 G1RegionMappingChangedListener _listener;
263 // The sequence of all heap regions in the heap.
264 HeapRegionManager _hrm;
266 // Class that handles the different kinds of allocations.
267 G1Allocator* _allocator;
269 // Statistics for each allocation context
270 AllocationContextStats _allocation_context_stats;
272 // PLAB sizing policy for survivors.
273 PLABStats _survivor_plab_stats;
275 // PLAB sizing policy for tenured objects.
276 PLABStats _old_plab_stats;
278 // It specifies whether we should attempt to expand the heap after a
279 // region allocation failure. If heap expansion fails we set this to
280 // false so that we don't re-attempt the heap expansion (it's likely
281 // that subsequent expansion attempts will also fail if one fails).
282 // Currently, it is only consulted during GC and it's reset at the
283 // start of each GC.
284 bool _expand_heap_after_alloc_failure;
286 // It resets the mutator alloc region before new allocations can take place.
287 void init_mutator_alloc_region();
289 // It releases the mutator alloc region.
290 void release_mutator_alloc_region();
292 // It initializes the GC alloc regions at the start of a GC.
293 void init_gc_alloc_regions(EvacuationInfo& evacuation_info);
295 // It releases the GC alloc regions at the end of a GC.
296 void release_gc_alloc_regions(uint no_of_gc_workers, EvacuationInfo& evacuation_info);
298 // It does any cleanup that needs to be done on the GC alloc regions
299 // before a Full GC.
300 void abandon_gc_alloc_regions();
302 // Helper for monitoring and management support.
303 G1MonitoringSupport* _g1mm;
305 // Records whether the region at the given index is (still) a
306 // candidate for eager reclaim. Only valid for humongous start
307 // regions; other regions have unspecified values. Humongous start
308 // regions are initialized at start of collection pause, with
309 // candidates removed from the set as they are found reachable from
310 // roots or the young generation.
311 class HumongousReclaimCandidates : public G1BiasedMappedArray<bool> {
312 protected:
313 bool default_value() const { return false; }
314 public:
315 void clear() { G1BiasedMappedArray<bool>::clear(); }
316 void set_candidate(uint region, bool value) {
317 set_by_index(region, value);
318 }
319 bool is_candidate(uint region) {
320 return get_by_index(region);
321 }
322 };
324 HumongousReclaimCandidates _humongous_reclaim_candidates;
325 // Stores whether during humongous object registration we found candidate regions.
326 // If not, we can skip a few steps.
327 bool _has_humongous_reclaim_candidates;
329 volatile unsigned _gc_time_stamp;
331 size_t* _surviving_young_words;
333 G1HRPrinter _hr_printer;
335 void setup_surviving_young_words();
336 void update_surviving_young_words(size_t* surv_young_words);
337 void cleanup_surviving_young_words();
339 // It decides whether an explicit GC should start a concurrent cycle
340 // instead of doing a STW GC. Currently, a concurrent cycle is
341 // explicitly started if:
342 // (a) cause == _gc_locker and +GCLockerInvokesConcurrent, or
343 // (b) cause == _java_lang_system_gc and +ExplicitGCInvokesConcurrent.
344 // (c) cause == _g1_humongous_allocation
345 bool should_do_concurrent_full_gc(GCCause::Cause cause);
347 // Keeps track of how many "old marking cycles" (i.e., Full GCs or
348 // concurrent cycles) we have started.
349 volatile uint _old_marking_cycles_started;
351 // Keeps track of how many "old marking cycles" (i.e., Full GCs or
352 // concurrent cycles) we have completed.
353 volatile uint _old_marking_cycles_completed;
355 bool _concurrent_cycle_started;
356 bool _heap_summary_sent;
358 // This is a non-product method that is helpful for testing. It is
359 // called at the end of a GC and artificially expands the heap by
360 // allocating a number of dead regions. This way we can induce very
361 // frequent marking cycles and stress the cleanup / concurrent
362 // cleanup code more (as all the regions that will be allocated by
363 // this method will be found dead by the marking cycle).
364 void allocate_dummy_regions() PRODUCT_RETURN;
366 // Clear RSets after a compaction. It also resets the GC time stamps.
367 void clear_rsets_post_compaction();
369 // If the HR printer is active, dump the state of the regions in the
370 // heap after a compaction.
371 void print_hrm_post_compaction();
373 // Create a memory mapper for auxiliary data structures of the given size and
374 // translation factor.
375 static G1RegionToSpaceMapper* create_aux_memory_mapper(const char* description,
376 size_t size,
377 size_t translation_factor);
379 void trace_heap(GCWhen::Type when, GCTracer* tracer);
381 double verify(bool guard, const char* msg);
382 void verify_before_gc();
383 void verify_after_gc();
385 void log_gc_header();
386 void log_gc_footer(double pause_time_sec);
388 // These are macros so that, if the assert fires, we get the correct
389 // line number, file, etc.
391 #define heap_locking_asserts_err_msg(_extra_message_) \
392 err_msg("%s : Heap_lock locked: %s, at safepoint: %s, is VM thread: %s", \
393 (_extra_message_), \
394 BOOL_TO_STR(Heap_lock->owned_by_self()), \
395 BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()), \
396 BOOL_TO_STR(Thread::current()->is_VM_thread()))
398 #define assert_heap_locked() \
399 do { \
400 assert(Heap_lock->owned_by_self(), \
401 heap_locking_asserts_err_msg("should be holding the Heap_lock")); \
402 } while (0)
404 #define assert_heap_locked_or_at_safepoint(_should_be_vm_thread_) \
405 do { \
406 assert(Heap_lock->owned_by_self() || \
407 (SafepointSynchronize::is_at_safepoint() && \
408 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread())), \
409 heap_locking_asserts_err_msg("should be holding the Heap_lock or " \
410 "should be at a safepoint")); \
411 } while (0)
413 #define assert_heap_locked_and_not_at_safepoint() \
414 do { \
415 assert(Heap_lock->owned_by_self() && \
416 !SafepointSynchronize::is_at_safepoint(), \
417 heap_locking_asserts_err_msg("should be holding the Heap_lock and " \
418 "should not be at a safepoint")); \
419 } while (0)
421 #define assert_heap_not_locked() \
422 do { \
423 assert(!Heap_lock->owned_by_self(), \
424 heap_locking_asserts_err_msg("should not be holding the Heap_lock")); \
425 } while (0)
427 #define assert_heap_not_locked_and_not_at_safepoint() \
428 do { \
429 assert(!Heap_lock->owned_by_self() && \
430 !SafepointSynchronize::is_at_safepoint(), \
431 heap_locking_asserts_err_msg("should not be holding the Heap_lock and " \
432 "should not be at a safepoint")); \
433 } while (0)
435 #define assert_at_safepoint(_should_be_vm_thread_) \
436 do { \
437 assert(SafepointSynchronize::is_at_safepoint() && \
438 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread()), \
439 heap_locking_asserts_err_msg("should be at a safepoint")); \
440 } while (0)
442 #define assert_not_at_safepoint() \
443 do { \
444 assert(!SafepointSynchronize::is_at_safepoint(), \
445 heap_locking_asserts_err_msg("should not be at a safepoint")); \
446 } while (0)
448 protected:
450 // The young region list.
451 YoungList* _young_list;
453 // The current policy object for the collector.
454 G1CollectorPolicy* _g1_policy;
456 // This is the second level of trying to allocate a new region. If
457 // new_region() didn't find a region on the free_list, this call will
458 // check whether there's anything available on the
459 // secondary_free_list and/or wait for more regions to appear on
460 // that list, if _free_regions_coming is set.
461 HeapRegion* new_region_try_secondary_free_list(bool is_old);
463 // Try to allocate a single non-humongous HeapRegion sufficient for
464 // an allocation of the given word_size. If do_expand is true,
465 // attempt to expand the heap if necessary to satisfy the allocation
466 // request. If the region is to be used as an old region or for a
467 // humongous object, set is_old to true. If not, to false.
468 HeapRegion* new_region(size_t word_size, bool is_old, bool do_expand);
470 // Initialize a contiguous set of free regions of length num_regions
471 // and starting at index first so that they appear as a single
472 // humongous region.
473 HeapWord* humongous_obj_allocate_initialize_regions(uint first,
474 uint num_regions,
475 size_t word_size,
476 AllocationContext_t context);
478 // Attempt to allocate a humongous object of the given size. Return
479 // NULL if unsuccessful.
480 HeapWord* humongous_obj_allocate(size_t word_size, AllocationContext_t context);
482 // The following two methods, allocate_new_tlab() and
483 // mem_allocate(), are the two main entry points from the runtime
484 // into the G1's allocation routines. They have the following
485 // assumptions:
486 //
487 // * They should both be called outside safepoints.
488 //
489 // * They should both be called without holding the Heap_lock.
490 //
491 // * All allocation requests for new TLABs should go to
492 // allocate_new_tlab().
493 //
494 // * All non-TLAB allocation requests should go to mem_allocate().
495 //
496 // * If either call cannot satisfy the allocation request using the
497 // current allocating region, they will try to get a new one. If
498 // this fails, they will attempt to do an evacuation pause and
499 // retry the allocation.
500 //
501 // * If all allocation attempts fail, even after trying to schedule
502 // an evacuation pause, allocate_new_tlab() will return NULL,
503 // whereas mem_allocate() will attempt a heap expansion and/or
504 // schedule a Full GC.
505 //
506 // * We do not allow humongous-sized TLABs. So, allocate_new_tlab
507 // should never be called with word_size being humongous. All
508 // humongous allocation requests should go to mem_allocate() which
509 // will satisfy them with a special path.
511 virtual HeapWord* allocate_new_tlab(size_t word_size);
513 virtual HeapWord* mem_allocate(size_t word_size,
514 bool* gc_overhead_limit_was_exceeded);
516 // The following three methods take a gc_count_before_ret
517 // parameter which is used to return the GC count if the method
518 // returns NULL. Given that we are required to read the GC count
519 // while holding the Heap_lock, and these paths will take the
520 // Heap_lock at some point, it's easier to get them to read the GC
521 // count while holding the Heap_lock before they return NULL instead
522 // of the caller (namely: mem_allocate()) having to also take the
523 // Heap_lock just to read the GC count.
525 // First-level mutator allocation attempt: try to allocate out of
526 // the mutator alloc region without taking the Heap_lock. This
527 // should only be used for non-humongous allocations.
528 inline HeapWord* attempt_allocation(size_t word_size,
529 uint* gc_count_before_ret,
530 uint* gclocker_retry_count_ret);
532 // Second-level mutator allocation attempt: take the Heap_lock and
533 // retry the allocation attempt, potentially scheduling a GC
534 // pause. This should only be used for non-humongous allocations.
535 HeapWord* attempt_allocation_slow(size_t word_size,
536 AllocationContext_t context,
537 uint* gc_count_before_ret,
538 uint* gclocker_retry_count_ret);
540 // Takes the Heap_lock and attempts a humongous allocation. It can
541 // potentially schedule a GC pause.
542 HeapWord* attempt_allocation_humongous(size_t word_size,
543 uint* gc_count_before_ret,
544 uint* gclocker_retry_count_ret);
546 // Allocation attempt that should be called during safepoints (e.g.,
547 // at the end of a successful GC). expect_null_mutator_alloc_region
548 // specifies whether the mutator alloc region is expected to be NULL
549 // or not.
550 HeapWord* attempt_allocation_at_safepoint(size_t word_size,
551 AllocationContext_t context,
552 bool expect_null_mutator_alloc_region);
554 // It dirties the cards that cover the block so that so that the post
555 // write barrier never queues anything when updating objects on this
556 // block. It is assumed (and in fact we assert) that the block
557 // belongs to a young region.
558 inline void dirty_young_block(HeapWord* start, size_t word_size);
560 // Allocate blocks during garbage collection. Will ensure an
561 // allocation region, either by picking one or expanding the
562 // heap, and then allocate a block of the given size. The block
563 // may not be a humongous - it must fit into a single heap region.
564 inline HeapWord* par_allocate_during_gc(InCSetState dest,
565 size_t word_size,
566 AllocationContext_t context);
567 // Ensure that no further allocations can happen in "r", bearing in mind
568 // that parallel threads might be attempting allocations.
569 void par_allocate_remaining_space(HeapRegion* r);
571 // Allocation attempt during GC for a survivor object / PLAB.
572 inline HeapWord* survivor_attempt_allocation(size_t word_size,
573 AllocationContext_t context);
575 // Allocation attempt during GC for an old object / PLAB.
576 inline HeapWord* old_attempt_allocation(size_t word_size,
577 AllocationContext_t context);
579 // These methods are the "callbacks" from the G1AllocRegion class.
581 // For mutator alloc regions.
582 HeapRegion* new_mutator_alloc_region(size_t word_size, bool force);
583 void retire_mutator_alloc_region(HeapRegion* alloc_region,
584 size_t allocated_bytes);
586 // For GC alloc regions.
587 HeapRegion* new_gc_alloc_region(size_t word_size, uint count,
588 InCSetState dest);
589 void retire_gc_alloc_region(HeapRegion* alloc_region,
590 size_t allocated_bytes, InCSetState dest);
592 // - if explicit_gc is true, the GC is for a System.gc() or a heap
593 // inspection request and should collect the entire heap
594 // - if clear_all_soft_refs is true, all soft references should be
595 // cleared during the GC
596 // - if explicit_gc is false, word_size describes the allocation that
597 // the GC should attempt (at least) to satisfy
598 // - it returns false if it is unable to do the collection due to the
599 // GC locker being active, true otherwise
600 bool do_collection(bool explicit_gc,
601 bool clear_all_soft_refs,
602 size_t word_size);
604 // Callback from VM_G1CollectFull operation.
605 // Perform a full collection.
606 virtual void do_full_collection(bool clear_all_soft_refs);
608 // Resize the heap if necessary after a full collection. If this is
609 // after a collect-for allocation, "word_size" is the allocation size,
610 // and will be considered part of the used portion of the heap.
611 void resize_if_necessary_after_full_collection(size_t word_size);
613 // Callback from VM_G1CollectForAllocation operation.
614 // This function does everything necessary/possible to satisfy a
615 // failed allocation request (including collection, expansion, etc.)
616 HeapWord* satisfy_failed_allocation(size_t word_size,
617 AllocationContext_t context,
618 bool* succeeded);
620 // Attempting to expand the heap sufficiently
621 // to support an allocation of the given "word_size". If
622 // successful, perform the allocation and return the address of the
623 // allocated block, or else "NULL".
624 HeapWord* expand_and_allocate(size_t word_size, AllocationContext_t context);
626 // Process any reference objects discovered during
627 // an incremental evacuation pause.
628 void process_discovered_references(uint no_of_gc_workers);
630 // Enqueue any remaining discovered references
631 // after processing.
632 void enqueue_discovered_references(uint no_of_gc_workers);
634 public:
636 G1Allocator* allocator() {
637 return _allocator;
638 }
640 G1MonitoringSupport* g1mm() {
641 assert(_g1mm != NULL, "should have been initialized");
642 return _g1mm;
643 }
645 // Expand the garbage-first heap by at least the given size (in bytes!).
646 // Returns true if the heap was expanded by the requested amount;
647 // false otherwise.
648 // (Rounds up to a HeapRegion boundary.)
649 bool expand(size_t expand_bytes);
651 // Returns the PLAB statistics for a given destination.
652 inline PLABStats* alloc_buffer_stats(InCSetState dest);
654 // Determines PLAB size for a given destination.
655 inline size_t desired_plab_sz(InCSetState dest);
657 inline AllocationContextStats& allocation_context_stats();
659 // Do anything common to GC's.
660 virtual void gc_prologue(bool full);
661 virtual void gc_epilogue(bool full);
663 // Modify the reclaim candidate set and test for presence.
664 // These are only valid for starts_humongous regions.
665 inline void set_humongous_reclaim_candidate(uint region, bool value);
666 inline bool is_humongous_reclaim_candidate(uint region);
668 // Remove from the reclaim candidate set. Also remove from the
669 // collection set so that later encounters avoid the slow path.
670 inline void set_humongous_is_live(oop obj);
672 // Register the given region to be part of the collection set.
673 inline void register_humongous_region_with_in_cset_fast_test(uint index);
674 // Register regions with humongous objects (actually on the start region) in
675 // the in_cset_fast_test table.
676 void register_humongous_regions_with_in_cset_fast_test();
677 // We register a region with the fast "in collection set" test. We
678 // simply set to true the array slot corresponding to this region.
679 void register_young_region_with_in_cset_fast_test(HeapRegion* r) {
680 _in_cset_fast_test.set_in_young(r->hrm_index());
681 }
682 void register_old_region_with_in_cset_fast_test(HeapRegion* r) {
683 _in_cset_fast_test.set_in_old(r->hrm_index());
684 }
686 // This is a fast test on whether a reference points into the
687 // collection set or not. Assume that the reference
688 // points into the heap.
689 inline bool in_cset_fast_test(oop obj);
691 void clear_cset_fast_test() {
692 _in_cset_fast_test.clear();
693 }
695 // This is called at the start of either a concurrent cycle or a Full
696 // GC to update the number of old marking cycles started.
697 void increment_old_marking_cycles_started();
699 // This is called at the end of either a concurrent cycle or a Full
700 // GC to update the number of old marking cycles completed. Those two
701 // can happen in a nested fashion, i.e., we start a concurrent
702 // cycle, a Full GC happens half-way through it which ends first,
703 // and then the cycle notices that a Full GC happened and ends
704 // too. The concurrent parameter is a boolean to help us do a bit
705 // tighter consistency checking in the method. If concurrent is
706 // false, the caller is the inner caller in the nesting (i.e., the
707 // Full GC). If concurrent is true, the caller is the outer caller
708 // in this nesting (i.e., the concurrent cycle). Further nesting is
709 // not currently supported. The end of this call also notifies
710 // the FullGCCount_lock in case a Java thread is waiting for a full
711 // GC to happen (e.g., it called System.gc() with
712 // +ExplicitGCInvokesConcurrent).
713 void increment_old_marking_cycles_completed(bool concurrent);
715 uint old_marking_cycles_completed() {
716 return _old_marking_cycles_completed;
717 }
719 void register_concurrent_cycle_start(const Ticks& start_time);
720 void register_concurrent_cycle_end();
721 void trace_heap_after_concurrent_cycle();
723 G1YCType yc_type();
725 G1HRPrinter* hr_printer() { return &_hr_printer; }
727 // Frees a non-humongous region by initializing its contents and
728 // adding it to the free list that's passed as a parameter (this is
729 // usually a local list which will be appended to the master free
730 // list later). The used bytes of freed regions are accumulated in
731 // pre_used. If par is true, the region's RSet will not be freed
732 // up. The assumption is that this will be done later.
733 // The locked parameter indicates if the caller has already taken
734 // care of proper synchronization. This may allow some optimizations.
735 void free_region(HeapRegion* hr,
736 FreeRegionList* free_list,
737 bool par,
738 bool locked = false);
740 // Frees a humongous region by collapsing it into individual regions
741 // and calling free_region() for each of them. The freed regions
742 // will be added to the free list that's passed as a parameter (this
743 // is usually a local list which will be appended to the master free
744 // list later). The used bytes of freed regions are accumulated in
745 // pre_used. If par is true, the region's RSet will not be freed
746 // up. The assumption is that this will be done later.
747 void free_humongous_region(HeapRegion* hr,
748 FreeRegionList* free_list,
749 bool par);
750 protected:
752 // Shrink the garbage-first heap by at most the given size (in bytes!).
753 // (Rounds down to a HeapRegion boundary.)
754 virtual void shrink(size_t expand_bytes);
755 void shrink_helper(size_t expand_bytes);
757 #if TASKQUEUE_STATS
758 static void print_taskqueue_stats_hdr(outputStream* const st = gclog_or_tty);
759 void print_taskqueue_stats(outputStream* const st = gclog_or_tty) const;
760 void reset_taskqueue_stats();
761 #endif // TASKQUEUE_STATS
763 // Schedule the VM operation that will do an evacuation pause to
764 // satisfy an allocation request of word_size. *succeeded will
765 // return whether the VM operation was successful (it did do an
766 // evacuation pause) or not (another thread beat us to it or the GC
767 // locker was active). Given that we should not be holding the
768 // Heap_lock when we enter this method, we will pass the
769 // gc_count_before (i.e., total_collections()) as a parameter since
770 // it has to be read while holding the Heap_lock. Currently, both
771 // methods that call do_collection_pause() release the Heap_lock
772 // before the call, so it's easy to read gc_count_before just before.
773 HeapWord* do_collection_pause(size_t word_size,
774 uint gc_count_before,
775 bool* succeeded,
776 GCCause::Cause gc_cause);
778 // The guts of the incremental collection pause, executed by the vm
779 // thread. It returns false if it is unable to do the collection due
780 // to the GC locker being active, true otherwise
781 bool do_collection_pause_at_safepoint(double target_pause_time_ms);
783 // Actually do the work of evacuating the collection set.
784 void evacuate_collection_set(EvacuationInfo& evacuation_info);
786 // The g1 remembered set of the heap.
787 G1RemSet* _g1_rem_set;
789 // A set of cards that cover the objects for which the Rsets should be updated
790 // concurrently after the collection.
791 DirtyCardQueueSet _dirty_card_queue_set;
793 // The closure used to refine a single card.
794 RefineCardTableEntryClosure* _refine_cte_cl;
796 // A function to check the consistency of dirty card logs.
797 void check_ct_logs_at_safepoint();
799 // A DirtyCardQueueSet that is used to hold cards that contain
800 // references into the current collection set. This is used to
801 // update the remembered sets of the regions in the collection
802 // set in the event of an evacuation failure.
803 DirtyCardQueueSet _into_cset_dirty_card_queue_set;
805 // After a collection pause, make the regions in the CS into free
806 // regions.
807 void free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info);
809 // Abandon the current collection set without recording policy
810 // statistics or updating free lists.
811 void abandon_collection_set(HeapRegion* cs_head);
813 // The concurrent marker (and the thread it runs in.)
814 ConcurrentMark* _cm;
815 ConcurrentMarkThread* _cmThread;
816 bool _mark_in_progress;
818 // The concurrent refiner.
819 ConcurrentG1Refine* _cg1r;
821 // The parallel task queues
822 RefToScanQueueSet *_task_queues;
824 // True iff a evacuation has failed in the current collection.
825 bool _evacuation_failed;
827 EvacuationFailedInfo* _evacuation_failed_info_array;
829 // Failed evacuations cause some logical from-space objects to have
830 // forwarding pointers to themselves. Reset them.
831 void remove_self_forwarding_pointers();
833 // Together, these store an object with a preserved mark, and its mark value.
834 Stack<oop, mtGC> _objs_with_preserved_marks;
835 Stack<markOop, mtGC> _preserved_marks_of_objs;
837 // Preserve the mark of "obj", if necessary, in preparation for its mark
838 // word being overwritten with a self-forwarding-pointer.
839 void preserve_mark_if_necessary(oop obj, markOop m);
841 // The stack of evac-failure objects left to be scanned.
842 GrowableArray<oop>* _evac_failure_scan_stack;
843 // The closure to apply to evac-failure objects.
845 OopsInHeapRegionClosure* _evac_failure_closure;
846 // Set the field above.
847 void
848 set_evac_failure_closure(OopsInHeapRegionClosure* evac_failure_closure) {
849 _evac_failure_closure = evac_failure_closure;
850 }
852 // Push "obj" on the scan stack.
853 void push_on_evac_failure_scan_stack(oop obj);
854 // Process scan stack entries until the stack is empty.
855 void drain_evac_failure_scan_stack();
856 // True iff an invocation of "drain_scan_stack" is in progress; to
857 // prevent unnecessary recursion.
858 bool _drain_in_progress;
860 // Do any necessary initialization for evacuation-failure handling.
861 // "cl" is the closure that will be used to process evac-failure
862 // objects.
863 void init_for_evac_failure(OopsInHeapRegionClosure* cl);
864 // Do any necessary cleanup for evacuation-failure handling data
865 // structures.
866 void finalize_for_evac_failure();
868 // An attempt to evacuate "obj" has failed; take necessary steps.
869 oop handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state, oop obj);
870 void handle_evacuation_failure_common(oop obj, markOop m);
872 #ifndef PRODUCT
873 // Support for forcing evacuation failures. Analogous to
874 // PromotionFailureALot for the other collectors.
876 // Records whether G1EvacuationFailureALot should be in effect
877 // for the current GC
878 bool _evacuation_failure_alot_for_current_gc;
880 // Used to record the GC number for interval checking when
881 // determining whether G1EvaucationFailureALot is in effect
882 // for the current GC.
883 size_t _evacuation_failure_alot_gc_number;
885 // Count of the number of evacuations between failures.
886 volatile size_t _evacuation_failure_alot_count;
888 // Set whether G1EvacuationFailureALot should be in effect
889 // for the current GC (based upon the type of GC and which
890 // command line flags are set);
891 inline bool evacuation_failure_alot_for_gc_type(bool gcs_are_young,
892 bool during_initial_mark,
893 bool during_marking);
895 inline void set_evacuation_failure_alot_for_current_gc();
897 // Return true if it's time to cause an evacuation failure.
898 inline bool evacuation_should_fail();
900 // Reset the G1EvacuationFailureALot counters. Should be called at
901 // the end of an evacuation pause in which an evacuation failure occurred.
902 inline void reset_evacuation_should_fail();
903 #endif // !PRODUCT
905 // ("Weak") Reference processing support.
906 //
907 // G1 has 2 instances of the reference processor class. One
908 // (_ref_processor_cm) handles reference object discovery
909 // and subsequent processing during concurrent marking cycles.
910 //
911 // The other (_ref_processor_stw) handles reference object
912 // discovery and processing during full GCs and incremental
913 // evacuation pauses.
914 //
915 // During an incremental pause, reference discovery will be
916 // temporarily disabled for _ref_processor_cm and will be
917 // enabled for _ref_processor_stw. At the end of the evacuation
918 // pause references discovered by _ref_processor_stw will be
919 // processed and discovery will be disabled. The previous
920 // setting for reference object discovery for _ref_processor_cm
921 // will be re-instated.
922 //
923 // At the start of marking:
924 // * Discovery by the CM ref processor is verified to be inactive
925 // and it's discovered lists are empty.
926 // * Discovery by the CM ref processor is then enabled.
927 //
928 // At the end of marking:
929 // * Any references on the CM ref processor's discovered
930 // lists are processed (possibly MT).
931 //
932 // At the start of full GC we:
933 // * Disable discovery by the CM ref processor and
934 // empty CM ref processor's discovered lists
935 // (without processing any entries).
936 // * Verify that the STW ref processor is inactive and it's
937 // discovered lists are empty.
938 // * Temporarily set STW ref processor discovery as single threaded.
939 // * Temporarily clear the STW ref processor's _is_alive_non_header
940 // field.
941 // * Finally enable discovery by the STW ref processor.
942 //
943 // The STW ref processor is used to record any discovered
944 // references during the full GC.
945 //
946 // At the end of a full GC we:
947 // * Enqueue any reference objects discovered by the STW ref processor
948 // that have non-live referents. This has the side-effect of
949 // making the STW ref processor inactive by disabling discovery.
950 // * Verify that the CM ref processor is still inactive
951 // and no references have been placed on it's discovered
952 // lists (also checked as a precondition during initial marking).
954 // The (stw) reference processor...
955 ReferenceProcessor* _ref_processor_stw;
957 STWGCTimer* _gc_timer_stw;
958 ConcurrentGCTimer* _gc_timer_cm;
960 G1OldTracer* _gc_tracer_cm;
961 G1NewTracer* _gc_tracer_stw;
963 // During reference object discovery, the _is_alive_non_header
964 // closure (if non-null) is applied to the referent object to
965 // determine whether the referent is live. If so then the
966 // reference object does not need to be 'discovered' and can
967 // be treated as a regular oop. This has the benefit of reducing
968 // the number of 'discovered' reference objects that need to
969 // be processed.
970 //
971 // Instance of the is_alive closure for embedding into the
972 // STW reference processor as the _is_alive_non_header field.
973 // Supplying a value for the _is_alive_non_header field is
974 // optional but doing so prevents unnecessary additions to
975 // the discovered lists during reference discovery.
976 G1STWIsAliveClosure _is_alive_closure_stw;
978 // The (concurrent marking) reference processor...
979 ReferenceProcessor* _ref_processor_cm;
981 // Instance of the concurrent mark is_alive closure for embedding
982 // into the Concurrent Marking reference processor as the
983 // _is_alive_non_header field. Supplying a value for the
984 // _is_alive_non_header field is optional but doing so prevents
985 // unnecessary additions to the discovered lists during reference
986 // discovery.
987 G1CMIsAliveClosure _is_alive_closure_cm;
989 // Cache used by G1CollectedHeap::start_cset_region_for_worker().
990 HeapRegion** _worker_cset_start_region;
992 // Time stamp to validate the regions recorded in the cache
993 // used by G1CollectedHeap::start_cset_region_for_worker().
994 // The heap region entry for a given worker is valid iff
995 // the associated time stamp value matches the current value
996 // of G1CollectedHeap::_gc_time_stamp.
997 uint* _worker_cset_start_region_time_stamp;
999 volatile bool _free_regions_coming;
1001 public:
1003 void set_refine_cte_cl_concurrency(bool concurrent);
1005 RefToScanQueue *task_queue(int i) const;
1007 // A set of cards where updates happened during the GC
1008 DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; }
1010 // A DirtyCardQueueSet that is used to hold cards that contain
1011 // references into the current collection set. This is used to
1012 // update the remembered sets of the regions in the collection
1013 // set in the event of an evacuation failure.
1014 DirtyCardQueueSet& into_cset_dirty_card_queue_set()
1015 { return _into_cset_dirty_card_queue_set; }
1017 // Create a G1CollectedHeap with the specified policy.
1018 // Must call the initialize method afterwards.
1019 // May not return if something goes wrong.
1020 G1CollectedHeap(G1CollectorPolicy* policy);
1022 // Initialize the G1CollectedHeap to have the initial and
1023 // maximum sizes and remembered and barrier sets
1024 // specified by the policy object.
1025 jint initialize();
1027 virtual void stop();
1029 // Return the (conservative) maximum heap alignment for any G1 heap
1030 static size_t conservative_max_heap_alignment();
1032 // Initialize weak reference processing.
1033 virtual void ref_processing_init();
1035 // Explicitly import set_par_threads into this scope
1036 using SharedHeap::set_par_threads;
1037 // Set _n_par_threads according to a policy TBD.
1038 void set_par_threads();
1040 virtual CollectedHeap::Name kind() const {
1041 return CollectedHeap::G1CollectedHeap;
1042 }
1044 // The current policy object for the collector.
1045 G1CollectorPolicy* g1_policy() const { return _g1_policy; }
1047 virtual CollectorPolicy* collector_policy() const { return (CollectorPolicy*) g1_policy(); }
1049 // Adaptive size policy. No such thing for g1.
1050 virtual AdaptiveSizePolicy* size_policy() { return NULL; }
1052 // The rem set and barrier set.
1053 G1RemSet* g1_rem_set() const { return _g1_rem_set; }
1055 unsigned get_gc_time_stamp() {
1056 return _gc_time_stamp;
1057 }
1059 inline void reset_gc_time_stamp();
1061 void check_gc_time_stamps() PRODUCT_RETURN;
1063 inline void increment_gc_time_stamp();
1065 // Reset the given region's GC timestamp. If it's starts humongous,
1066 // also reset the GC timestamp of its corresponding
1067 // continues humongous regions too.
1068 void reset_gc_time_stamps(HeapRegion* hr);
1070 void iterate_dirty_card_closure(CardTableEntryClosure* cl,
1071 DirtyCardQueue* into_cset_dcq,
1072 bool concurrent, uint worker_i);
1074 // The shared block offset table array.
1075 G1BlockOffsetSharedArray* bot_shared() const { return _bot_shared; }
1077 // Reference Processing accessors
1079 // The STW reference processor....
1080 ReferenceProcessor* ref_processor_stw() const { return _ref_processor_stw; }
1082 // The Concurrent Marking reference processor...
1083 ReferenceProcessor* ref_processor_cm() const { return _ref_processor_cm; }
1085 ConcurrentGCTimer* gc_timer_cm() const { return _gc_timer_cm; }
1086 G1OldTracer* gc_tracer_cm() const { return _gc_tracer_cm; }
1088 virtual size_t capacity() const;
1089 virtual size_t used() const;
1090 // This should be called when we're not holding the heap lock. The
1091 // result might be a bit inaccurate.
1092 size_t used_unlocked() const;
1093 size_t recalculate_used() const;
1095 // These virtual functions do the actual allocation.
1096 // Some heaps may offer a contiguous region for shared non-blocking
1097 // allocation, via inlined code (by exporting the address of the top and
1098 // end fields defining the extent of the contiguous allocation region.)
1099 // But G1CollectedHeap doesn't yet support this.
1101 virtual bool is_maximal_no_gc() const {
1102 return _hrm.available() == 0;
1103 }
1105 // The current number of regions in the heap.
1106 uint num_regions() const { return _hrm.length(); }
1108 // The max number of regions in the heap.
1109 uint max_regions() const { return _hrm.max_length(); }
1111 // The number of regions that are completely free.
1112 uint num_free_regions() const { return _hrm.num_free_regions(); }
1114 MemoryUsage get_auxiliary_data_memory_usage() const {
1115 return _hrm.get_auxiliary_data_memory_usage();
1116 }
1118 // The number of regions that are not completely free.
1119 uint num_used_regions() const { return num_regions() - num_free_regions(); }
1121 void verify_not_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
1122 void verify_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
1123 void verify_dirty_young_list(HeapRegion* head) PRODUCT_RETURN;
1124 void verify_dirty_young_regions() PRODUCT_RETURN;
1126 #ifndef PRODUCT
1127 // Make sure that the given bitmap has no marked objects in the
1128 // range [from,limit). If it does, print an error message and return
1129 // false. Otherwise, just return true. bitmap_name should be "prev"
1130 // or "next".
1131 bool verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap,
1132 HeapWord* from, HeapWord* limit);
1134 // Verify that the prev / next bitmap range [tams,end) for the given
1135 // region has no marks. Return true if all is well, false if errors
1136 // are detected.
1137 bool verify_bitmaps(const char* caller, HeapRegion* hr);
1138 #endif // PRODUCT
1140 // If G1VerifyBitmaps is set, verify that the marking bitmaps for
1141 // the given region do not have any spurious marks. If errors are
1142 // detected, print appropriate error messages and crash.
1143 void check_bitmaps(const char* caller, HeapRegion* hr) PRODUCT_RETURN;
1145 // If G1VerifyBitmaps is set, verify that the marking bitmaps do not
1146 // have any spurious marks. If errors are detected, print
1147 // appropriate error messages and crash.
1148 void check_bitmaps(const char* caller) PRODUCT_RETURN;
1150 // Do sanity check on the contents of the in-cset fast test table.
1151 bool check_cset_fast_test() PRODUCT_RETURN_( return true; );
1153 // verify_region_sets() performs verification over the region
1154 // lists. It will be compiled in the product code to be used when
1155 // necessary (i.e., during heap verification).
1156 void verify_region_sets();
1158 // verify_region_sets_optional() is planted in the code for
1159 // list verification in non-product builds (and it can be enabled in
1160 // product builds by defining HEAP_REGION_SET_FORCE_VERIFY to be 1).
1161 #if HEAP_REGION_SET_FORCE_VERIFY
1162 void verify_region_sets_optional() {
1163 verify_region_sets();
1164 }
1165 #else // HEAP_REGION_SET_FORCE_VERIFY
1166 void verify_region_sets_optional() { }
1167 #endif // HEAP_REGION_SET_FORCE_VERIFY
1169 #ifdef ASSERT
1170 bool is_on_master_free_list(HeapRegion* hr) {
1171 return _hrm.is_free(hr);
1172 }
1173 #endif // ASSERT
1175 // Wrapper for the region list operations that can be called from
1176 // methods outside this class.
1178 void secondary_free_list_add(FreeRegionList* list) {
1179 _secondary_free_list.add_ordered(list);
1180 }
1182 void append_secondary_free_list() {
1183 _hrm.insert_list_into_free_list(&_secondary_free_list);
1184 }
1186 void append_secondary_free_list_if_not_empty_with_lock() {
1187 // If the secondary free list looks empty there's no reason to
1188 // take the lock and then try to append it.
1189 if (!_secondary_free_list.is_empty()) {
1190 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
1191 append_secondary_free_list();
1192 }
1193 }
1195 inline void old_set_remove(HeapRegion* hr);
1197 size_t non_young_capacity_bytes() {
1198 return _old_set.total_capacity_bytes() + _humongous_set.total_capacity_bytes();
1199 }
1201 void set_free_regions_coming();
1202 void reset_free_regions_coming();
1203 bool free_regions_coming() { return _free_regions_coming; }
1204 void wait_while_free_regions_coming();
1206 // Determine whether the given region is one that we are using as an
1207 // old GC alloc region.
1208 bool is_old_gc_alloc_region(HeapRegion* hr) {
1209 return _allocator->is_retained_old_region(hr);
1210 }
1212 // Perform a collection of the heap; intended for use in implementing
1213 // "System.gc". This probably implies as full a collection as the
1214 // "CollectedHeap" supports.
1215 virtual void collect(GCCause::Cause cause);
1217 // The same as above but assume that the caller holds the Heap_lock.
1218 void collect_locked(GCCause::Cause cause);
1220 virtual bool copy_allocation_context_stats(const jint* contexts,
1221 jlong* totals,
1222 jbyte* accuracy,
1223 jint len);
1225 // True iff an evacuation has failed in the most-recent collection.
1226 bool evacuation_failed() { return _evacuation_failed; }
1228 void remove_from_old_sets(const HeapRegionSetCount& old_regions_removed, const HeapRegionSetCount& humongous_regions_removed);
1229 void prepend_to_freelist(FreeRegionList* list);
1230 void decrement_summary_bytes(size_t bytes);
1232 // Returns "TRUE" iff "p" points into the committed areas of the heap.
1233 virtual bool is_in(const void* p) const;
1234 #ifdef ASSERT
1235 // Returns whether p is in one of the available areas of the heap. Slow but
1236 // extensive version.
1237 bool is_in_exact(const void* p) const;
1238 #endif
1240 // Return "TRUE" iff the given object address is within the collection
1241 // set. Slow implementation.
1242 inline bool obj_in_cs(oop obj);
1244 inline bool is_in_cset(oop obj);
1246 inline bool is_in_cset_or_humongous(const oop obj);
1248 private:
1249 // This array is used for a quick test on whether a reference points into
1250 // the collection set or not. Each of the array's elements denotes whether the
1251 // corresponding region is in the collection set or not.
1252 G1InCSetStateFastTestBiasedMappedArray _in_cset_fast_test;
1254 public:
1256 inline InCSetState in_cset_state(const oop obj);
1258 // Return "TRUE" iff the given object address is in the reserved
1259 // region of g1.
1260 bool is_in_g1_reserved(const void* p) const {
1261 return _hrm.reserved().contains(p);
1262 }
1264 // Returns a MemRegion that corresponds to the space that has been
1265 // reserved for the heap
1266 MemRegion g1_reserved() const {
1267 return _hrm.reserved();
1268 }
1270 virtual bool is_in_closed_subset(const void* p) const;
1272 G1SATBCardTableLoggingModRefBS* g1_barrier_set() {
1273 return (G1SATBCardTableLoggingModRefBS*) barrier_set();
1274 }
1276 // This resets the card table to all zeros. It is used after
1277 // a collection pause which used the card table to claim cards.
1278 void cleanUpCardTable();
1280 // Iteration functions.
1282 // Iterate over all the ref-containing fields of all objects, calling
1283 // "cl.do_oop" on each.
1284 virtual void oop_iterate(ExtendedOopClosure* cl);
1286 // Iterate over all objects, calling "cl.do_object" on each.
1287 virtual void object_iterate(ObjectClosure* cl);
1289 virtual void safe_object_iterate(ObjectClosure* cl) {
1290 object_iterate(cl);
1291 }
1293 // Iterate over all spaces in use in the heap, in ascending address order.
1294 virtual void space_iterate(SpaceClosure* cl);
1296 // Iterate over heap regions, in address order, terminating the
1297 // iteration early if the "doHeapRegion" method returns "true".
1298 void heap_region_iterate(HeapRegionClosure* blk) const;
1300 // Return the region with the given index. It assumes the index is valid.
1301 inline HeapRegion* region_at(uint index) const;
1303 // Calculate the region index of the given address. Given address must be
1304 // within the heap.
1305 inline uint addr_to_region(HeapWord* addr) const;
1307 inline HeapWord* bottom_addr_for_region(uint index) const;
1309 // Divide the heap region sequence into "chunks" of some size (the number
1310 // of regions divided by the number of parallel threads times some
1311 // overpartition factor, currently 4). Assumes that this will be called
1312 // in parallel by ParallelGCThreads worker threads with discinct worker
1313 // ids in the range [0..max(ParallelGCThreads-1, 1)], that all parallel
1314 // calls will use the same "claim_value", and that that claim value is
1315 // different from the claim_value of any heap region before the start of
1316 // the iteration. Applies "blk->doHeapRegion" to each of the regions, by
1317 // attempting to claim the first region in each chunk, and, if
1318 // successful, applying the closure to each region in the chunk (and
1319 // setting the claim value of the second and subsequent regions of the
1320 // chunk.) For now requires that "doHeapRegion" always returns "false",
1321 // i.e., that a closure never attempt to abort a traversal.
1322 void heap_region_par_iterate_chunked(HeapRegionClosure* cl,
1323 uint worker_id,
1324 uint num_workers,
1325 jint claim_value) const;
1327 // It resets all the region claim values to the default.
1328 void reset_heap_region_claim_values();
1330 // Resets the claim values of regions in the current
1331 // collection set to the default.
1332 void reset_cset_heap_region_claim_values();
1334 #ifdef ASSERT
1335 bool check_heap_region_claim_values(jint claim_value);
1337 // Same as the routine above but only checks regions in the
1338 // current collection set.
1339 bool check_cset_heap_region_claim_values(jint claim_value);
1340 #endif // ASSERT
1342 // Clear the cached cset start regions and (more importantly)
1343 // the time stamps. Called when we reset the GC time stamp.
1344 void clear_cset_start_regions();
1346 // Given the id of a worker, obtain or calculate a suitable
1347 // starting region for iterating over the current collection set.
1348 HeapRegion* start_cset_region_for_worker(uint worker_i);
1350 // Iterate over the regions (if any) in the current collection set.
1351 void collection_set_iterate(HeapRegionClosure* blk);
1353 // As above but starting from region r
1354 void collection_set_iterate_from(HeapRegion* r, HeapRegionClosure *blk);
1356 HeapRegion* next_compaction_region(const HeapRegion* from) const;
1358 // A CollectedHeap will contain some number of spaces. This finds the
1359 // space containing a given address, or else returns NULL.
1360 virtual Space* space_containing(const void* addr) const;
1362 // Returns the HeapRegion that contains addr. addr must not be NULL.
1363 template <class T>
1364 inline HeapRegion* heap_region_containing_raw(const T addr) const;
1366 // Returns the HeapRegion that contains addr. addr must not be NULL.
1367 // If addr is within a humongous continues region, it returns its humongous start region.
1368 template <class T>
1369 inline HeapRegion* heap_region_containing(const T addr) const;
1371 // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
1372 // each address in the (reserved) heap is a member of exactly
1373 // one block. The defining characteristic of a block is that it is
1374 // possible to find its size, and thus to progress forward to the next
1375 // block. (Blocks may be of different sizes.) Thus, blocks may
1376 // represent Java objects, or they might be free blocks in a
1377 // free-list-based heap (or subheap), as long as the two kinds are
1378 // distinguishable and the size of each is determinable.
1380 // Returns the address of the start of the "block" that contains the
1381 // address "addr". We say "blocks" instead of "object" since some heaps
1382 // may not pack objects densely; a chunk may either be an object or a
1383 // non-object.
1384 virtual HeapWord* block_start(const void* addr) const;
1386 // Requires "addr" to be the start of a chunk, and returns its size.
1387 // "addr + size" is required to be the start of a new chunk, or the end
1388 // of the active area of the heap.
1389 virtual size_t block_size(const HeapWord* addr) const;
1391 // Requires "addr" to be the start of a block, and returns "TRUE" iff
1392 // the block is an object.
1393 virtual bool block_is_obj(const HeapWord* addr) const;
1395 // Does this heap support heap inspection? (+PrintClassHistogram)
1396 virtual bool supports_heap_inspection() const { return true; }
1398 // Section on thread-local allocation buffers (TLABs)
1399 // See CollectedHeap for semantics.
1401 bool supports_tlab_allocation() const;
1402 size_t tlab_capacity(Thread* ignored) const;
1403 size_t tlab_used(Thread* ignored) const;
1404 size_t max_tlab_size() const;
1405 size_t unsafe_max_tlab_alloc(Thread* ignored) const;
1407 // Can a compiler initialize a new object without store barriers?
1408 // This permission only extends from the creation of a new object
1409 // via a TLAB up to the first subsequent safepoint. If such permission
1410 // is granted for this heap type, the compiler promises to call
1411 // defer_store_barrier() below on any slow path allocation of
1412 // a new object for which such initializing store barriers will
1413 // have been elided. G1, like CMS, allows this, but should be
1414 // ready to provide a compensating write barrier as necessary
1415 // if that storage came out of a non-young region. The efficiency
1416 // of this implementation depends crucially on being able to
1417 // answer very efficiently in constant time whether a piece of
1418 // storage in the heap comes from a young region or not.
1419 // See ReduceInitialCardMarks.
1420 virtual bool can_elide_tlab_store_barriers() const {
1421 return true;
1422 }
1424 virtual bool card_mark_must_follow_store() const {
1425 return true;
1426 }
1428 inline bool is_in_young(const oop obj);
1430 #ifdef ASSERT
1431 virtual bool is_in_partial_collection(const void* p);
1432 #endif
1434 virtual bool is_scavengable(const void* addr);
1436 // We don't need barriers for initializing stores to objects
1437 // in the young gen: for the SATB pre-barrier, there is no
1438 // pre-value that needs to be remembered; for the remembered-set
1439 // update logging post-barrier, we don't maintain remembered set
1440 // information for young gen objects.
1441 virtual inline bool can_elide_initializing_store_barrier(oop new_obj);
1443 // Returns "true" iff the given word_size is "very large".
1444 static bool isHumongous(size_t word_size) {
1445 // Note this has to be strictly greater-than as the TLABs
1446 // are capped at the humongous thresold and we want to
1447 // ensure that we don't try to allocate a TLAB as
1448 // humongous and that we don't allocate a humongous
1449 // object in a TLAB.
1450 return word_size > _humongous_object_threshold_in_words;
1451 }
1453 // Update mod union table with the set of dirty cards.
1454 void updateModUnion();
1456 // Set the mod union bits corresponding to the given memRegion. Note
1457 // that this is always a safe operation, since it doesn't clear any
1458 // bits.
1459 void markModUnionRange(MemRegion mr);
1461 // Records the fact that a marking phase is no longer in progress.
1462 void set_marking_complete() {
1463 _mark_in_progress = false;
1464 }
1465 void set_marking_started() {
1466 _mark_in_progress = true;
1467 }
1468 bool mark_in_progress() {
1469 return _mark_in_progress;
1470 }
1472 // Print the maximum heap capacity.
1473 virtual size_t max_capacity() const;
1475 virtual jlong millis_since_last_gc();
1478 // Convenience function to be used in situations where the heap type can be
1479 // asserted to be this type.
1480 static G1CollectedHeap* heap();
1482 void set_region_short_lived_locked(HeapRegion* hr);
1483 // add appropriate methods for any other surv rate groups
1485 YoungList* young_list() const { return _young_list; }
1487 // debugging
1488 bool check_young_list_well_formed() {
1489 return _young_list->check_list_well_formed();
1490 }
1492 bool check_young_list_empty(bool check_heap,
1493 bool check_sample = true);
1495 // *** Stuff related to concurrent marking. It's not clear to me that so
1496 // many of these need to be public.
1498 // The functions below are helper functions that a subclass of
1499 // "CollectedHeap" can use in the implementation of its virtual
1500 // functions.
1501 // This performs a concurrent marking of the live objects in a
1502 // bitmap off to the side.
1503 void doConcurrentMark();
1505 bool isMarkedPrev(oop obj) const;
1506 bool isMarkedNext(oop obj) const;
1508 // Determine if an object is dead, given the object and also
1509 // the region to which the object belongs. An object is dead
1510 // iff a) it was not allocated since the last mark and b) it
1511 // is not marked.
1512 bool is_obj_dead(const oop obj, const HeapRegion* hr) const {
1513 return
1514 !hr->obj_allocated_since_prev_marking(obj) &&
1515 !isMarkedPrev(obj);
1516 }
1518 // This function returns true when an object has been
1519 // around since the previous marking and hasn't yet
1520 // been marked during this marking.
1521 bool is_obj_ill(const oop obj, const HeapRegion* hr) const {
1522 return
1523 !hr->obj_allocated_since_next_marking(obj) &&
1524 !isMarkedNext(obj);
1525 }
1527 // Determine if an object is dead, given only the object itself.
1528 // This will find the region to which the object belongs and
1529 // then call the region version of the same function.
1531 // Added if it is NULL it isn't dead.
1533 inline bool is_obj_dead(const oop obj) const;
1535 inline bool is_obj_ill(const oop obj) const;
1537 bool allocated_since_marking(oop obj, HeapRegion* hr, VerifyOption vo);
1538 HeapWord* top_at_mark_start(HeapRegion* hr, VerifyOption vo);
1539 bool is_marked(oop obj, VerifyOption vo);
1540 const char* top_at_mark_start_str(VerifyOption vo);
1542 ConcurrentMark* concurrent_mark() const { return _cm; }
1544 // Refinement
1546 ConcurrentG1Refine* concurrent_g1_refine() const { return _cg1r; }
1548 // The dirty cards region list is used to record a subset of regions
1549 // whose cards need clearing. The list if populated during the
1550 // remembered set scanning and drained during the card table
1551 // cleanup. Although the methods are reentrant, population/draining
1552 // phases must not overlap. For synchronization purposes the last
1553 // element on the list points to itself.
1554 HeapRegion* _dirty_cards_region_list;
1555 void push_dirty_cards_region(HeapRegion* hr);
1556 HeapRegion* pop_dirty_cards_region();
1558 // Optimized nmethod scanning support routines
1560 // Register the given nmethod with the G1 heap
1561 virtual void register_nmethod(nmethod* nm);
1563 // Unregister the given nmethod from the G1 heap
1564 virtual void unregister_nmethod(nmethod* nm);
1566 // Free up superfluous code root memory.
1567 void purge_code_root_memory();
1569 // Rebuild the stong code root lists for each region
1570 // after a full GC
1571 void rebuild_strong_code_roots();
1573 // Delete entries for dead interned string and clean up unreferenced symbols
1574 // in symbol table, possibly in parallel.
1575 void unlink_string_and_symbol_table(BoolObjectClosure* is_alive, bool unlink_strings = true, bool unlink_symbols = true);
1577 // Parallel phase of unloading/cleaning after G1 concurrent mark.
1578 void parallel_cleaning(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool class_unloading_occurred);
1580 // Redirty logged cards in the refinement queue.
1581 void redirty_logged_cards();
1582 // Verification
1584 // The following is just to alert the verification code
1585 // that a full collection has occurred and that the
1586 // remembered sets are no longer up to date.
1587 bool _full_collection;
1588 void set_full_collection() { _full_collection = true;}
1589 void clear_full_collection() {_full_collection = false;}
1590 bool full_collection() {return _full_collection;}
1592 // Perform any cleanup actions necessary before allowing a verification.
1593 virtual void prepare_for_verify();
1595 // Perform verification.
1597 // vo == UsePrevMarking -> use "prev" marking information,
1598 // vo == UseNextMarking -> use "next" marking information
1599 // vo == UseMarkWord -> use the mark word in the object header
1600 //
1601 // NOTE: Only the "prev" marking information is guaranteed to be
1602 // consistent most of the time, so most calls to this should use
1603 // vo == UsePrevMarking.
1604 // Currently, there is only one case where this is called with
1605 // vo == UseNextMarking, which is to verify the "next" marking
1606 // information at the end of remark.
1607 // Currently there is only one place where this is called with
1608 // vo == UseMarkWord, which is to verify the marking during a
1609 // full GC.
1610 void verify(bool silent, VerifyOption vo);
1612 // Override; it uses the "prev" marking information
1613 virtual void verify(bool silent);
1615 // The methods below are here for convenience and dispatch the
1616 // appropriate method depending on value of the given VerifyOption
1617 // parameter. The values for that parameter, and their meanings,
1618 // are the same as those above.
1620 bool is_obj_dead_cond(const oop obj,
1621 const HeapRegion* hr,
1622 const VerifyOption vo) const;
1624 bool is_obj_dead_cond(const oop obj,
1625 const VerifyOption vo) const;
1627 G1HeapSummary create_g1_heap_summary();
1629 // Printing
1631 virtual void print_on(outputStream* st) const;
1632 virtual void print_extended_on(outputStream* st) const;
1633 virtual void print_on_error(outputStream* st) const;
1635 virtual void print_gc_threads_on(outputStream* st) const;
1636 virtual void gc_threads_do(ThreadClosure* tc) const;
1638 // Override
1639 void print_tracing_info() const;
1641 // The following two methods are helpful for debugging RSet issues.
1642 void print_cset_rsets() PRODUCT_RETURN;
1643 void print_all_rsets() PRODUCT_RETURN;
1645 public:
1646 size_t pending_card_num();
1647 size_t cards_scanned();
1649 protected:
1650 size_t _max_heap_capacity;
1651 };
1653 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP